1. Field of the Invention
The present invention generally relates to graphics processing unit (GPU), and, more specifically, to a method and system for supplying an output voltage to a graphics processing unit.
2. Description of the Related Art
In a typical computer system, one or more power supply subsystems are configured to supply voltages to the various system components in the computer system. For example, a first power supply subsystem may supply a first voltage to a first processing unit (e.g., central processing unit), and a second power supply subsystem may supply a second voltage to a second processing unit (e.g., graphics processing unit) of a graphics subsystem within the computer system.
Pulse-width modulation (PWM) is one of the techniques utilized in the second power supply subsystem for a graphics processing unit (GPU). Specifically, this second power supply subsystem may adjust an output voltage to the GPU based on a PWM signal. To adjust the output voltage to the GPU, the second power supply subsystem may also include a feedback mechanism having a voltage divider to prepare a predetermined percentage of the output voltage to the GPU. The second power supply subsystem then compares this predetermined percentage of the output voltage with a reference voltage before generating the PWM signal. And the second power supply subsystem may further utilize the PWM signal to adjust the output voltage to the GPU. With usage of the voltage divider, the second power supply subsystem may introduce undesirable voltage spikes or voltage undershoots.
FIG. 1 illustrates an example computer system 100 having a PWM-based power supply subsystem 110 for providing an output voltage to a GPU 120. The power supply subsystem 110 comprises a voltage regulator 130, an error amplifier (EA) 140, a PWM circuit 150 having a gate logic 160, and a feedback (FB) circuit 164. The PWM circuit 150 may supply a first voltage signal 163 as an output voltage to the GPU 120. The FB circuit 164 may further include a voltage divider 165. The FB circuit 164 may be configured to receive the first voltage signal 163. With the voltage divider 165, the FB circuit 164 may prepare a feedback voltage signal 166, which is a predetermined percentage of the first voltage signal 163. And the feedback signal 166 may be received by the EA 140. The EA 140 is further configured to receive a second voltage signal 168 from the voltage regulator 130. The EA 140 may generate a difference signal 172 indicating a duty cycle according to the difference between the second voltage signal 168 and the feedback signal 166. The PWM circuit 150 may further receive the difference signal 172 before preparing the first voltage signal 163.
At least one disadvantage associated with the power supply subsystem 110 is the possibility of occurrences of voltage spikes or voltage undershoots during dynamic voltage change. As previously mentioned, the power supply subsystem 110 outputs the first voltage signal 163 according to the feedback signal 166 which is prepared solely based on the operation of the voltage divider 165. Therefore, regardless of how carefully the voltage divider 165 is designed, the feedback signal 166 may spike or undershoot as the result of the voltage divider 165. And the spike or undershoot may erroneously skew the difference signal 172, which further affects the output of the first voltage signal 163.
As the foregoing illustrates, what is needed in the art is thus a method and apparatus for providing a voltage to a GPU while reducing the likelihood of experiencing voltage spikes or voltage undershoots and address at least one of the foregoing issues.